获取字符串字节数

/**
 获取字符串  字节数

 @return 返回字节数
 
 备注：1.getCharasLength方法写在NSString 分类中
    2.NSUInteger charsNum = [regexStr getCharasLength];
 */
- (NSUInteger)getCharasLength {
    NSStringEncoding encoding = CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingGB_18030_2000);
    return [self getCharasLengthWithEncoding:encoding];
}

- (NSUInteger)getCharasLengthWithEncoding:(NSStringEncoding)encoding {
    
    NSUInteger strLength = 0;
    char *q = (char *)[self cStringUsingEncoding:encoding];
    
    NSUInteger lengthBytes = [self lengthOfBytesUsingEncoding:encoding];
    for (int i = 0; i < lengthBytes; i++) {
        if (*q) {
            q++;
            strLength++;
        }
        else {
            q++;
        }
    }
    return strLength;
}